<!DOCTYPE html>



  


<html class="theme-next mist use-motion" lang="zh-Hans">
<head><meta name="generator" content="Hexo 3.8.0">
  <meta charset="UTF-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">
<meta name="theme-color" content="#222">









<meta http-equiv="Cache-Control" content="no-transform">
<meta http-equiv="Cache-Control" content="no-siteapp">
















  
  
  <link href="/lib/fancybox/source/jquery.fancybox.css?v=2.1.5" rel="stylesheet" type="text/css">







<link href="/lib/font-awesome/css/font-awesome.min.css?v=4.6.2" rel="stylesheet" type="text/css">

<link href="/css/main.css?v=5.1.4" rel="stylesheet" type="text/css">


  <link rel="apple-touch-icon" sizes="180x180" href="/images/apple-touch-icon-next.png?v=5.1.4">


  <link rel="icon" type="image/png" sizes="32x32" href="/images/favicon-32x32-next.png?v=5.1.4">


  <link rel="icon" type="image/png" sizes="16x16" href="/images/favicon-16x16-next.png?v=5.1.4">


  <link rel="mask-icon" href="/images/logo.svg?v=5.1.4" color="#222">





  <meta name="keywords" content="Hexo, NexT">










<meta name="description" content="C++类前置声明会造成内存泄漏的问题总结先上代码12345678910111213141516171819202122232425262728293031323334353637class A;class B&amp;#123;public:    B()    &amp;#123;        cout &amp;lt;&amp;lt; &amp;quot;B()&amp;quot; &amp;lt;&amp;lt; endl;    &amp;#125;">
<meta property="og:type" content="article">
<meta property="og:title" content="c++不完全对象造成内存泄漏">
<meta property="og:url" content="http://yoursite.com/2017/08/11/c-不完全对象造成内存泄漏/index.html">
<meta property="og:site_name" content="vicvon&#39;s blog">
<meta property="og:description" content="C++类前置声明会造成内存泄漏的问题总结先上代码12345678910111213141516171819202122232425262728293031323334353637class A;class B&amp;#123;public:    B()    &amp;#123;        cout &amp;lt;&amp;lt; &amp;quot;B()&amp;quot; &amp;lt;&amp;lt; endl;    &amp;#125;">
<meta property="og:locale" content="zh-Hans">
<meta property="og:updated_time" content="2018-10-24T12:46:30.212Z">
<meta name="twitter:card" content="summary">
<meta name="twitter:title" content="c++不完全对象造成内存泄漏">
<meta name="twitter:description" content="C++类前置声明会造成内存泄漏的问题总结先上代码12345678910111213141516171819202122232425262728293031323334353637class A;class B&amp;#123;public:    B()    &amp;#123;        cout &amp;lt;&amp;lt; &amp;quot;B()&amp;quot; &amp;lt;&amp;lt; endl;    &amp;#125;">



<script type="text/javascript" id="hexo.configurations">
  var NexT = window.NexT || {};
  var CONFIG = {
    root: '/',
    scheme: 'Mist',
    version: '5.1.4',
    sidebar: {"position":"left","display":"post","offset":12,"b2t":false,"scrollpercent":false,"onmobile":false},
    fancybox: true,
    tabs: true,
    motion: {"enable":true,"async":false,"transition":{"post_block":"fadeIn","post_header":"slideDownIn","post_body":"slideDownIn","coll_header":"slideLeftIn","sidebar":"slideUpIn"}},
    duoshuo: {
      userId: '0',
      author: '博主'
    },
    algolia: {
      applicationID: '',
      apiKey: '',
      indexName: '',
      hits: {"per_page":10},
      labels: {"input_placeholder":"Search for Posts","hits_empty":"We didn't find any results for the search: ${query}","hits_stats":"${hits} results found in ${time} ms"}
    }
  };
</script>



  <link rel="canonical" href="http://yoursite.com/2017/08/11/c-不完全对象造成内存泄漏/">





  <title>c++不完全对象造成内存泄漏 | vicvon's blog</title>
  








</head>

<body itemscope="" itemtype="http://schema.org/WebPage" lang="zh-Hans">

  
  
    
  

  <div class="container sidebar-position-left page-post-detail">
    <div class="headband"></div>

    <header id="header" class="header" itemscope="" itemtype="http://schema.org/WPHeader">
      <div class="header-inner"><div class="site-brand-wrapper">
  <div class="site-meta ">
    

    <div class="custom-logo-site-title">
      <a href="/" class="brand" rel="start">
        <span class="logo-line-before"><i></i></span>
        <span class="site-title">vicvon's blog</span>
        <span class="logo-line-after"><i></i></span>
      </a>
    </div>
      
        <p class="site-subtitle"></p>
      
  </div>

  <div class="site-nav-toggle">
    <button>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
      <span class="btn-bar"></span>
    </button>
  </div>
</div>

<nav class="site-nav">
  

  
    <ul id="menu" class="menu">
      
        
        <li class="menu-item menu-item-home">
          <a href="/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-home"></i> <br>
            
            首页
          </a>
        </li>
      
        
        <li class="menu-item menu-item-categories">
          <a href="/categories/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-th"></i> <br>
            
            分类
          </a>
        </li>
      
        
        <li class="menu-item menu-item-about">
          <a href="/about/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-user"></i> <br>
            
            关于
          </a>
        </li>
      
        
        <li class="menu-item menu-item-archives">
          <a href="/archives/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-archive"></i> <br>
            
            归档
          </a>
        </li>
      
        
        <li class="menu-item menu-item-tags">
          <a href="/tags/" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-tags"></i> <br>
            
            标签
          </a>
        </li>
      
        
        <li class="menu-item menu-item-sitemap">
          <a href="/sitemap.xml" rel="section">
            
              <i class="menu-item-icon fa fa-fw fa-sitemap"></i> <br>
            
            站点地图
          </a>
        </li>
      

      
    </ul>
  

  
</nav>



 </div>
    </header>

    <main id="main" class="main">
      <div class="main-inner">
        <div class="content-wrap">
          <div id="content" class="content">
            

  <div id="posts" class="posts-expand">
    

  

  
  
  

  <article class="post post-type-normal" itemscope="" itemtype="http://schema.org/Article">
  
  
  
  <div class="post-block">
    <link itemprop="mainEntityOfPage" href="http://yoursite.com/2017/08/11/c-不完全对象造成内存泄漏/">

    <span hidden itemprop="author" itemscope="" itemtype="http://schema.org/Person">
      <meta itemprop="name" content="vicvon">
      <meta itemprop="description" content="">
      <meta itemprop="image" content="/uploads/avatar.jpg">
    </span>

    <span hidden itemprop="publisher" itemscope="" itemtype="http://schema.org/Organization">
      <meta itemprop="name" content="vicvon's blog">
    </span>

    
      <header class="post-header">

        
        
          <h1 class="post-title" itemprop="name headline">c++不完全对象造成内存泄漏</h1>
        

        <div class="post-meta">
          <span class="post-time">
            
              <span class="post-meta-item-icon">
                <i class="fa fa-calendar-o"></i>
              </span>
              
                <span class="post-meta-item-text">发表于</span>
              
              <time title="创建于" itemprop="dateCreated datePublished" datetime="2017-08-11T14:21:49+08:00">
                2017-08-11
              </time>
            

            

            
          </span>

          
            <span class="post-category">
            
              <span class="post-meta-divider">|</span>
            
              <span class="post-meta-item-icon">
                <i class="fa fa-folder-o"></i>
              </span>
              
                <span class="post-meta-item-text">分类于</span>
              
              
                <span itemprop="about" itemscope="" itemtype="http://schema.org/Thing">
                  <a href="/categories/cplusplus/" itemprop="url" rel="index">
                    <span itemprop="name">cplusplus</span>
                  </a>
                </span>

                
                
              
            </span>
          

          
            
              <span class="post-comments-count">
                <span class="post-meta-divider">|</span>
                <span class="post-meta-item-icon">
                  <i class="fa fa-comment-o"></i>
                </span>
                <a href="/2017/08/11/c-不完全对象造成内存泄漏/#comments" itemprop="discussionUrl">
                  <span class="post-comments-count disqus-comment-count" data-disqus-identifier="2017/08/11/c-不完全对象造成内存泄漏/" itemprop="commentCount"></span>
                </a>
              </span>
            
          

          
          

          

          

          

        </div>
      </header>
    

    
    
    
    <div class="post-body" itemprop="articleBody">

      
      

      
        <h5 id="C-类前置声明会造成内存泄漏的问题总结"><a href="#C-类前置声明会造成内存泄漏的问题总结" class="headerlink" title="C++类前置声明会造成内存泄漏的问题总结"></a>C++类前置声明会造成内存泄漏的问题总结</h5><p>先上代码<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br><span class="line">36</span><br><span class="line">37</span><br></pre></td><td class="code"><pre><span class="line">class A;</span><br><span class="line"></span><br><span class="line">class B</span><br><span class="line">&#123;</span><br><span class="line">public:</span><br><span class="line">    B()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;B()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    ~B()</span><br><span class="line">    &#123;</span><br><span class="line">        delete a;</span><br><span class="line">        cout &lt;&lt; &quot;~B()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    A *a;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line">class A</span><br><span class="line">&#123;</span><br><span class="line">public:</span><br><span class="line">    A()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;A()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    ~A()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;~A()&quot; endl;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line">int main()</span><br><span class="line">&#123;</span><br><span class="line">    A *aa = new A();</span><br><span class="line">    B *bb = new B();</span><br><span class="line">    bb-&gt;a = aa;</span><br><span class="line">    delete bb;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p>这种情况会导致A无法析构，造成内存泄漏。</p>
<p>再上一份代码<br><figure class="highlight plain"><table><tr><td class="gutter"><pre><span class="line">1</span><br><span class="line">2</span><br><span class="line">3</span><br><span class="line">4</span><br><span class="line">5</span><br><span class="line">6</span><br><span class="line">7</span><br><span class="line">8</span><br><span class="line">9</span><br><span class="line">10</span><br><span class="line">11</span><br><span class="line">12</span><br><span class="line">13</span><br><span class="line">14</span><br><span class="line">15</span><br><span class="line">16</span><br><span class="line">17</span><br><span class="line">18</span><br><span class="line">19</span><br><span class="line">20</span><br><span class="line">21</span><br><span class="line">22</span><br><span class="line">23</span><br><span class="line">24</span><br><span class="line">25</span><br><span class="line">26</span><br><span class="line">27</span><br><span class="line">28</span><br><span class="line">29</span><br><span class="line">30</span><br><span class="line">31</span><br><span class="line">32</span><br><span class="line">33</span><br><span class="line">34</span><br><span class="line">35</span><br></pre></td><td class="code"><pre><span class="line">class A</span><br><span class="line">&#123;</span><br><span class="line">public:</span><br><span class="line">    A()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;A()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    ~A()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;~A()&quot; endl;</span><br><span class="line">    &#125;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line">class B</span><br><span class="line">&#123;</span><br><span class="line">public:</span><br><span class="line">    B()</span><br><span class="line">    &#123;</span><br><span class="line">        cout &lt;&lt; &quot;B()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    ~B()</span><br><span class="line">    &#123;</span><br><span class="line">        delete a;</span><br><span class="line">        cout &lt;&lt; &quot;~B()&quot; &lt;&lt; endl;</span><br><span class="line">    &#125;</span><br><span class="line">    A *a;</span><br><span class="line">&#125;;</span><br><span class="line"></span><br><span class="line">int main()</span><br><span class="line">&#123;</span><br><span class="line">    A *aa = new A();</span><br><span class="line">    B *bb = new B();</span><br><span class="line">    bb-&gt;a = aa;</span><br><span class="line">    delete bb;</span><br><span class="line">&#125;</span><br></pre></td></tr></table></figure></p>
<p>这样A就可以正常析构了。<br>造成内存泄漏的原因是前置声明的类用delete属于未定义的行为。</p>

      
    </div>
    
    
    

    

    

    

    <footer class="post-footer">
      

      
      
      

      
        <div class="post-nav">
          <div class="post-nav-next post-nav-item">
            
              <a href="/2017/08/11/c-返回引用和const引用的问题/" rel="next" title="c++返回引用和const引用的问题">
                <i class="fa fa-chevron-left"></i> c++返回引用和const引用的问题
              </a>
            
          </div>

          <span class="post-nav-divider"></span>

          <div class="post-nav-prev post-nav-item">
            
              <a href="/2017/08/11/shared-ptr循环引用的分析/" rel="prev" title="shared_ptr循环引用的分析">
                shared_ptr循环引用的分析 <i class="fa fa-chevron-right"></i>
              </a>
            
          </div>
        </div>
      

      
      
    </footer>
  </div>
  
  
  
  </article>



    <div class="post-spread">
      
    </div>
  </div>


          </div>
          


          

  
    <div class="comments" id="comments">
      <div id="disqus_thread">
        <noscript>
          Please enable JavaScript to view the
          <a href="https://disqus.com/?ref_noscript">comments powered by Disqus.</a>
        </noscript>
      </div>
    </div>

  



        </div>
        
          
  
  <div class="sidebar-toggle">
    <div class="sidebar-toggle-line-wrap">
      <span class="sidebar-toggle-line sidebar-toggle-line-first"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-middle"></span>
      <span class="sidebar-toggle-line sidebar-toggle-line-last"></span>
    </div>
  </div>

  <aside id="sidebar" class="sidebar">
    
    <div class="sidebar-inner">

      

      
        <ul class="sidebar-nav motion-element">
          <li class="sidebar-nav-toc sidebar-nav-active" data-target="post-toc-wrap">
            文章目录
          </li>
          <li class="sidebar-nav-overview" data-target="site-overview-wrap">
            站点概览
          </li>
        </ul>
      

      <section class="site-overview-wrap sidebar-panel">
        <div class="site-overview">
          <div class="site-author motion-element" itemprop="author" itemscope="" itemtype="http://schema.org/Person">
            
              <img class="site-author-image" itemprop="image" src="/uploads/avatar.jpg" alt="vicvon">
            
              <p class="site-author-name" itemprop="name">vicvon</p>
              <p class="site-description motion-element" itemprop="description">记录点滴，慢慢成长</p>
          </div>

          <nav class="site-state motion-element">

            
              <div class="site-state-item site-state-posts">
              
                <a href="/archives/">
              
                  <span class="site-state-item-count">27</span>
                  <span class="site-state-item-name">日志</span>
                </a>
              </div>
            

            
              
              
              <div class="site-state-item site-state-categories">
                <a href="/categories/index.html">
                  <span class="site-state-item-count">6</span>
                  <span class="site-state-item-name">分类</span>
                </a>
              </div>
            

            
              
              
              <div class="site-state-item site-state-tags">
                <a href="/tags/index.html">
                  <span class="site-state-item-count">1</span>
                  <span class="site-state-item-name">标签</span>
                </a>
              </div>
            

          </nav>

          

          
            <div class="links-of-author motion-element">
                
                  <span class="links-of-author-item">
                    <a href="https://github.com/vicvon" target="_blank" title="GitHub">
                      
                        <i class="fa fa-fw fa-github"></i>GitHub</a>
                  </span>
                
            </div>
          

          
          

          
          

          

        </div>
      </section>

      
      <!--noindex-->
        <section class="post-toc-wrap motion-element sidebar-panel sidebar-panel-active">
          <div class="post-toc">

            
              
            

            
              <div class="post-toc-content"><ol class="nav"><li class="nav-item nav-level-5"><a class="nav-link" href="#C-类前置声明会造成内存泄漏的问题总结"><span class="nav-number">1.</span> <span class="nav-text">C++类前置声明会造成内存泄漏的问题总结</span></a></li></ol></div>
            

          </div>
        </section>
      <!--/noindex-->
      

      

    </div>
  </aside>


        
      </div>
    </main>

    <footer id="footer" class="footer">
      <div class="footer-inner">
        <div class="copyright">&copy; <span itemprop="copyrightYear">2019</span>
  <span class="with-love">
    <i class="fa fa-heart"></i>
  </span>
  <span class="author" itemprop="copyrightHolder">true</span>

  
</div>


  <div class="powered-by">由 <a class="theme-link" target="_blank" href="https://hexo.io">Hexo</a> 强力驱动</div>



  <span class="post-meta-divider">|</span>



  <div class="theme-info">主题 &mdash; <a class="theme-link" target="_blank" href="https://github.com/iissnan/hexo-theme-next">NexT.Mist</a> v5.1.4</div>




        




  <script type="text/javascript">
    (function() {
      var hm = document.createElement("script");
      hm.src = "//tajs.qq.com/stats?sId=63333898";
      var s = document.getElementsByTagName("script")[0];
      s.parentNode.insertBefore(hm, s);
    })();
  </script>




        
      </div>
    </footer>

    
      <div class="back-to-top">
        <i class="fa fa-arrow-up"></i>
        
      </div>
    

    

  </div>

  

<script type="text/javascript">
  if (Object.prototype.toString.call(window.Promise) !== '[object Function]') {
    window.Promise = null;
  }
</script>









  












  
  
    <script type="text/javascript" src="/lib/jquery/index.js?v=2.1.3"></script>
  

  
  
    <script type="text/javascript" src="/lib/fastclick/lib/fastclick.min.js?v=1.0.6"></script>
  

  
  
    <script type="text/javascript" src="/lib/jquery_lazyload/jquery.lazyload.js?v=1.9.7"></script>
  

  
  
    <script type="text/javascript" src="/lib/velocity/velocity.min.js?v=1.2.1"></script>
  

  
  
    <script type="text/javascript" src="/lib/velocity/velocity.ui.min.js?v=1.2.1"></script>
  

  
  
    <script type="text/javascript" src="/lib/fancybox/source/jquery.fancybox.pack.js?v=2.1.5"></script>
  


  


  <script type="text/javascript" src="/js/src/utils.js?v=5.1.4"></script>

  <script type="text/javascript" src="/js/src/motion.js?v=5.1.4"></script>



  
  

  
  <script type="text/javascript" src="/js/src/scrollspy.js?v=5.1.4"></script>
<script type="text/javascript" src="/js/src/post-details.js?v=5.1.4"></script>



  


  <script type="text/javascript" src="/js/src/bootstrap.js?v=5.1.4"></script>



  


  

    
      <script id="dsq-count-scr" src="https://vicvon1.disqus.com/count.js" async></script>
    

    
      <script type="text/javascript">
        var disqus_config = function () {
          this.page.url = 'http://yoursite.com/2017/08/11/c-不完全对象造成内存泄漏/';
          this.page.identifier = '2017/08/11/c-不完全对象造成内存泄漏/';
          this.page.title = 'c++不完全对象造成内存泄漏';
        };
        var d = document, s = d.createElement('script');
        s.src = 'https://vicvon1.disqus.com/embed.js';
        s.setAttribute('data-timestamp', '' + +new Date());
        (d.head || d.body).appendChild(s);
      </script>
    

  




	





  














  





  

  

  

  
  

  

  

  

</body>
</html>
